1. Field of the Invention
The present invention relates to an image reading apparatus and image reading method. More particularly, the present invention relates to an image reading apparatus and image reading method that enables image data to be input via a relatively low-rate communication channel such as a wireless communication network.
2. Description of the Related Art
In recent years, in place of a printer that can be used only for printing, a multifunctional peripheral (MFP) integrating a function of scanner with a printer has come into wide use. Such an MFP may be connected to an apparatus that can execute image processing, such as a personal computer (PC) and the like, to execute reading of a high-resolution full-color image. In addition, since the MFP can be used also as an independent apparatus, such as a copying machine or a facsimile machine, that does not need to be connected to a PC, there is also a strong demand for installing MFPs at locations away from a PC rather than near a PC. For these and other reasons, it is expected that the cases requiring a high degree of freedom of installation will increase. As a substitute for connection that enables a high-speed data transfer by means of cables suitable for data transfer in close-range such as SCSI, IEEE1394, and USB2.0, which are conventionally used for connection between PCs and image reading apparatuses, it is expected that cases will increase in which a wireless local-area network (LAN) represented by IEEE802.11a/b/g, electric power line communication (PLC), and the like will be used for connections between image reading apparatus and PCs.
However, these wireless connection methods have lower data transfer rates than many conventional wired methods. On the other hand, the resolution of an image to be read has become higher as the performance of image reading apparatuses has increased, and thus the amount of image data to be transmitted tends to increase. For instance, when a full-color image (RGB 24 bits) in A4 size is read at 600 dpi, the amount of non-compressed data reaches nearly 100 M bytes. USB2.0 (which typically has transfer rate of about ten to fifteen M bytes per second (10-15 MB/s)) is now widely used for connection of a scanner or an MFP to a computer. USB2.0 typically can transfer 100 M bytes in a few seconds. Thus, using USB2.0, the transfer of a 100 M byte image is completed substantially at the same time as the completion of the reading operation. However, in wireless LAN (which typically has a transfer rate of a few MB/s), approximately 100 seconds is required for data transfer.
Since the reading operation of the image reading apparatus is completed in about 20 seconds, users have to wait until the data transfer is completed for a few tens of seconds even after the reading operation has been completed. Also, although the length of time which a user has to wait for a single image may be acceptable to the user, for a plurality of images to be scanned sequentially, the waiting time increases in rough proportion to the number of images, which raises a problem that the user has to wait for a long time to receive the desired images. Frequently, the time needed to transfer image data winds up being wasted by the user as it is difficult to switch back and forth between tasks.
Thus, in an existing image reading system that is supposed to employ a connection form that can perform a high-rate communication, it is difficult to provide a comfortable image reading function to a user in an image reading system that is connected via a low-rate communication channel. In connection forms in which scanned image data with such huge-volumes of data needs to pass by way of a communication channel with a low data transfer rate, several methods to improve the efficiency of image reading jobs and to provide a user-friendly system have been proposed.
For example, in a system where a PC and an image reading apparatus are connected via a network, image data that an image reading apparatus has read is stored in an image server. Then, the PC firstly acquires thumbnail images with small data amount that is stored in the image server, and subsequently acquires, from the image server, only read image data of desired images. Japanese Patent Application Laid-Open No. 11-317833 discusses a technique to reduce the amount of data to be transferred to a PC with such an operation. Also, in a system to which large-capacity external storage devices are connected, that can directly read and write data via IEEE1394, etc., from the PC and the image reading apparatus, read image data is directly transferred from the image reading apparatus to an external storage device, and only a part of the read image data is transferred to the PC. Japanese Patent Application Laid-Open No. 11-205517 discusses a technique to reduce the amount of data to be transferred to a PC with such an operation.
However, techniques discussed at present have not yet solved image data transfer problems for users. These techniques require users to make different operations from that of image reading jobs commonly performed at present. Further, it is difficult to perform optimal image processing for acquiring high-quality read images. In general, in a reading job, first, a preview is executed of an image that has been read at a first resolution to read an image for grasping the overview of readable images. Image data to be read in the preview typically is of low resolution so that the preview can be displayed more quickly on a display device, such as a CRT or a liquid crystal monitor, provided in an image processing apparatus such as a PC.
For this reason, the number of pixels of 600 to 900 in the vertical and horizontal directions of the preview image respectively, or approximately 2 M bytes in terms of data amount is enough, and even if a connection form between a PC and an MFP is a low-rate communication channel, substantially no problems occurs. Users select and adjust, while viewing a displayed preview image, the range of image reading for save and image processing to be performed on the read image, which are the final objects of the processing. By selecting and adjusting such image processing, images that have been subjected to selected/adjusted image processing, with respect to the preview image, can be displayed on the display device.
Then, after the selected and adjusted image is confirmed by viewing the preview image, final image reading is instructed, and image data that has been read at a second resolution that is generally higher than a first resolution will be saved as a designated file. Hereinafter, image data that has been read in this manner is referred to as “image data-for-save”. Lossy compression can be applied to the image data-for-save, but in many cases, lossless compression (compression without losses of information) is applied thereto. Even when the lossy compression is applied to the image data-for-save, a suppressed compression ratio is employed to keep the quality of the image data high.
By performing such a process, reading only an image within a designated reading range is sufficient for the image reading apparatus, and consequently a time required for the reading operation can be reduced to the requisite minimum. Also, after confirming the effect by viewing the preview image, a suitable image processing can be applied to the images for save. In image processing that is applied to the images for save, there is processing that should be performed in an image reading apparatus and processing that is suitably performed in an image processing apparatus. For example, it is suitable to perform such processing that is needed to be performed by using information that an image sensor has read, such as color shift correction, in the image reading apparatus. On the other hand, it is suitable to perform such processing that will need a large amount of memory and a central processing unit (CPU) of high speed, such as automatic color correction, in an image processing apparatus such as a PC. In the conventional process, it is possible to perform various image processes image reading apparatus and others in the image processing apparatus.
However, in the techniques discussed in Japanese Patent Application Laid-Open No. 11-317833, a read image is saved in a server or an external storage device, and a thumbnail image of the read image or a part of the image is transmitted to a PC. Conventionally, it is neither possible to select a reading area using the displayed thumbnail image or a part of the image, nor to select/adjust image processing to be applied to the read-image. Also, in the technique discussed in Japanese Patent Application Laid-Open No. 11-317833, users need to be conscious of whether an image reading apparatus is directly connected to an image processing apparatus or rather connected via a network. Different operations are performed depending on whether the network is used. For example, in connection via the network, users have to conduct an operation on a PC to acquire desired image data stored in an image server, that is, an operation that is not needed in direct connection. In addition, in the technique discussed in Japanese Patent Application Laid-Open No. 11-205517, image data that has been read is transferred from an image reading apparatus via IEEE1394 to an external storage device, and image data that has been read is not even transferred to a PC. Because the PC does not receive such image data, an image processing that needs a large amount of memory and a high speed CPU, such as automatic color correction, for example, cannot readily be performed.
Compressing a read image for save using a method, which can reduce data amount considerably, such as JPEG, may be available. However, the compression methods which can reduce the data amount sufficiently are lossy, in which the original complete image cannot be decompressed, and thus unsuitable when a high-quality read image is desired. On the other hand, in a lossless compression, in which a complete image can be decompressed, although some images can be heavily compressed, there are no techniques for adequately reducing the data amount suitable for the wide variety of images that most users need to be able to process.